package com.hyq.responsibility;
/**
* @ClassName: Logger 
* @Description: 责任链模式 -- 来自于维基百科
* @author Janus
 */
abstract class Logger 
{
    public static int ERR = 3;
    public static int NOTICE = 5;
    public static int DEBUG = 7;
    protected int mask;

    // The next element in the chain of responsibility
    protected Logger next;
    public Logger setNext( Logger l)
    {
        next = l;
        return this;
    }

    public final void message( String msg, int priority )
    {
        if ( priority <= mask ) 
        {
            writeMessage( msg );
            if ( next != null )
            {
                next.message( msg, priority );
            }
        }
    }
    
    protected abstract void writeMessage( String msg );

}

class StdoutLogger extends Logger 
{

    public StdoutLogger( int mask ) { this.mask = mask; }

    protected void writeMessage( String msg )
    {
        System.out.println( "Writting to stdout: " + msg );
    }
}


class EmailLogger extends Logger 
{

    public EmailLogger( int mask ) { this.mask = mask; }

    protected void writeMessage( String msg )
    {
        System.out.println( "Sending via email: " + msg );
    }
}

class StderrLogger extends Logger 
{

    public StderrLogger( int mask ) { this.mask = mask; }

    protected void writeMessage( String msg )
    {
        System.out.println( "Sending to stderr: " + msg );
    }
}

public class ChainOfResponsibilityExample
{
    public static void main( String[] args )
    {
        // Build the chain of responsibility
        Logger l = new StdoutLogger( Logger.DEBUG).setNext(
                            new EmailLogger( Logger.NOTICE ).setNext(
                            new StderrLogger( Logger.ERR ) ) );

        // Handled by StdoutLogger
        l.message( "Entering function y.", Logger.DEBUG );

        // Handled by StdoutLogger and EmailLogger
        l.message( "Step1 completed.", Logger.NOTICE );

        // Handled by all three loggers
        l.message( "An error has occurred.", Logger.ERR );
    }
}
